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Precise and accurate mass and radius measurements of evolved stars are crucial to calibrating stellar models. Stars in detached eclipsing binaries (EBs) are excellent potential calibrators because their stellar parameters can be measured with fractional uncertainties of a few percent, independent of stellar models. The All-Sky Automated Survey for Supernovae (ASAS-SN) has identified tens of thousands of EBs, >35,000 of which were included in the ASAS-SN eclipsing binaries catalog. Here, we select eight EBs from this sample that contain giants based on their Gaia colors and absolute magnitudes. We use LBT/PEPSI, APF, and CHIRON to obtain multi-epoch spectra of these binaries and measure their radial velocities using two-dimensional cross-correlation methods. We simultaneously fit the ASAS-SN light curves and the radial velocities with PHOEBE to derive accurate and precise masses and radii with fractional uncertainties of $\lesssim 3\%$. For four systems, we also include Transiting Exoplanet Survey Satellite (TESS) light curves in our PHOEBE models, which significantly improves the radius determinations. In seven of our systems, both components have evolved off of the main sequence, and one system has a giant star component with a main sequence, Sun-like companion. Finally, we compare our mass and radius measurements to single-star evolutionary tracks and distinguish between systems that are first ascent red giant branch stars and those that are likely core helium-burning stars. 

Abstract Stellar spin down is a critical yet poorly understood component of stellar evolution. In particular, results from the Kepler Mission imply that mature age, solar-type stars have inefficient magnetic braking, resulting in a stalled spin-down rate. However, a large number of precise asteroseismic ages are needed for mature (≥3 Gyr) stars in order to probe the regime where traditional and stalled spin-down models differ. In this paper, we present a new asteroseismic benchmark star for gyrochronology discovered using reprocessed Kepler short cadence data. KIC 11029516 (Papayu) is a bright (Kp= 9.6 mag) solar-type star with a well-measured rotation period (21.1 ± 0.8 days) from spot modulation using 4 yr of Kepler long-cadence data. We combine asteroseismology and spectroscopy to obtainT_eff= 5888 ± 100 K, [Fe/H] = 0.30 ± 0.06 dex,M= 1.24 ± 0.05M_⊙,R= 1.34 ± 0.02R_⊙, and age of 4.0 ± 0.4 Gyr, making Papayu one of the most similar stars to the Sun in terms of temperature and radius with an asteroseismic age and a rotation period measured from spot modulation. We find that Papayu sits at the transition of where traditional and weakened spin-down models diverge. A comparison with stars of similar zero-age main-sequence temperatures supports previous findings that weakened spin-down models are required to explain the ages and rotation periods of old solar-type stars. 

ABSTRACT The identification and characterization of massive (≳ 0.8 M⊙) white dwarfs is challenging in part due to their low luminosity. Here, we present two candidate single-lined spectroscopic binaries, Gaia DR3 4014708864481651840 and 5811237403155163520, with K-dwarf primaries and optically dark companions. Both have orbital periods of P ∼ 0.45 d and show rotational variability, ellipsoidal modulations, and high-amplitude radial velocity variations. Using light curves from the Transiting Exoplanet Survey Satellite (TESS), radial velocities from ground-based spectrographs, and spectral energy distributions, we characterize these binaries to describe the nature of the unseen companion. We find that both systems are consistent with a massive white dwarf companion. Unlike simple ellipsoidal variables, star-spots cause the light-curve morphology to change between TESS sectors. We attempt to constrain the orbital inclination using phoebe binary light-curve models, but degeneracies in the light curves of spotted stars prevent a precise determination. Finally, we search for similar objects using Gaia DR3 and TESS, and comment on these systems in the context of recently claimed compact object binaries. 

Abstract A stable-frequency transmitter with relative radial acceleration to a receiver will show a change in received frequency over time, known as a “drift rate.” For a transmission from an exoplanet, we must account for multiple components of drift rate: the exoplanet’s orbit and rotation, the Earth’s orbit and rotation, and other contributions. Understanding the drift rate distribution produced by exoplanets relative to Earth, can (a) help us constrain the range of drift rates to check in a Search for Extraterrestrial Intelligence project to detect radio technosignatures, and (b) help us decide validity of signals-of-interest, as we can compare drifting signals with expected drift rates from the target star. In this paper, we modeled the drift rate distribution for ∼5300 confirmed exoplanets, using parameters from the NASA Exoplanet Archive (NEA). We find that confirmed exoplanets have drift rates such that 99% of them fall within the ±53 nHz range. This implies a distribution-informed maximum drift rate ∼4 times lower than previous work. To mitigate the observational biases inherent in the NEA, we also simulated an exoplanet population built to reduce these biases. The results suggest that, for a Kepler-like target star without known exoplanets, ±0.44 nHz would be sufficient to account for 99% of signals. This reduction in recommended maximum drift rate is partially due to inclination effects and bias toward short orbital periods in the NEA. These narrowed drift rate maxima will increase the efficiency of searches and save significant computational effort in future radio technosignature searches. 

Abstract We present high-precision radial velocity observations of Gaia BH1, the nearest known black hole (BH). The system contains a solar-type G star orbiting a massive dark companion, which could be either a single BH or an inner BH + BH binary. A BH + BH binary is expected in some models where Gaia BH1 formed as a hierarchical triple, which is attractive because they avoid many of the difficulties associated with forming the system through isolated binary evolution. Our observations test the inner binary scenario. We have measured 115 precise RVs of the G star, including 40 from ESPRESSO with a precision of 3–5 m s⁻¹, and 75 from other instruments with a typical precision of 30–100 m s⁻¹. Our observations span 2.33 orbits of the G star and are concentrated near a periastron passage, when perturbations due to an inner binary would be largest. The RVs are well-fit by a Keplerian two-body orbit and show no convincing evidence of an inner binary. UsingREBOUNDsimulations of hierarchical triples with a range of inner periods, mass ratios, eccentricities, and orientations, we show that plausible inner binaries with periodsP_inner≳ 1.5 days would have produced larger deviations from a Keplerian orbit than observed. Binaries withP_inner≲ 1.5 days are consistent with the data, but these would merge within a Hubble time and would thus imply fine-tuning. We present updated parameters of Gaia BH1's orbit. The RVs yield a spectroscopic mass function $f\left(M_{\mathrm{BH}}\right)=3.9358\pm 0.0002M_{\odot }$—about 7000σabove the ∼2.5M_⊙maximum neutron star mass. Including the inclination constraint from Gaia astrometry, this implies a BH mass ofM_BH= 9.27 ± 0.10M_⊙. 

Abstract The Search for Extraterrestrial Intelligence has traditionally been conducted at radio wavelengths, but optical searches are well-motivated and increasingly feasible due to the growing availability of high-resolution spectroscopy. We present a data analysis pipeline to search Automated Planet Finder (APF) spectroscopic observations from the Levy Spectrometer for intense, persistent, narrow-bandwidth optical lasers. We describe the processing of the spectra, the laser search algorithm, and the results of our laser search on 1983 spectra of 388 stars as part of the Breakthrough Listen search for technosignatures. We utilize an empirical spectra-matching algorithm calledSpecMatch-Empto produce residuals between each target spectrum and a set of best-matching catalog spectra, which provides the basis for a more sensitive search than previously possible. We verify thatSpecMatch-Empperforms well on APF-Levy spectra by calibrating the stellar properties derived by the algorithm against theSpecMatch-Emplibrary and against Gaia catalog values. We leverage our unique observing strategy, which produces multiple spectra of each target per night of observing, to increase our detection sensitivity by programmatically rejecting events that do not persist between observations. With our laser search algorithm, we achieve a sensitivity equivalent to the ability to detect an 84 kW laser at the median distance of a star in our data set (78.5 ly). We present the methodology and vetting of our laser search, finding no convincing candidates consistent with potential laser emission in our target sample. 

Abstract The Breakthrough Listen search for intelligent life is, to date, the most extensive technosignature search of nearby celestial objects. We present a radio technosignature search of the centers of 97 nearby galaxies, observed by Breakthrough Listen at the Robert C. Byrd Green Bank Telescope. We performed a narrowband Doppler drift search using theturboSETIpipeline with a minimum signal-to-noise parameter threshold of 10, across a drift rate range of ±4 Hz s⁻¹, with a spectral resolution of 3 Hz and a time resolution of ∼18.25 s. We removed radio frequency interference (RFI) by using an on-source/off-source cadence pattern of six observations and discarding signals with Doppler drift rates of 0. We assess factors affecting the sensitivity of the Breakthrough Listen data reduction and search pipeline using signal injection and recovery techniques and apply new methods for the investigation of the RFI environment. We present results in four frequency bands covering 1–11 GHz, and place constraints on the presence of transmitters with equivalent isotropic radiated power on the order of 10²⁶W, corresponding to the theoretical power consumption of Kardashev Type II civilizations. 

Abstract Wolf 359 (CN Leo, GJ 406, Gaia DR3 3864972938605115520) is a low-mass star in the fifth-closest neighboring system (2.41 pc). Because of its relative youth and proximity, Wolf 359 offers a unique opportunity to study substellar companions around M stars using infrared high-contrast imaging and radial velocity monitoring. We present the results ofMs-band (4.67μm) vector vortex coronagraphic imaging using Keck-NIRC2 and add 12 Keck-HIRES and 68 MAROON-X velocities to the radial velocity baseline. Our analysis incorporates these data alongside literature radial velocities from CARMENES, the High Accuracy Radial velocity Planet Searcher, and Keck-HIRES to rule out the existence of a close (a< 10 au) stellar or brown dwarf companion and the majority of large gas giant companions. Our survey does not refute or confirm the long-period radial velocity candidate, Wolf 359 b (P∼ 2900 days), but rules out the candidate's existence as a large gas giant (>4M_Jup) assuming an age of younger than 1 Gyr. We discuss the performance of our high-contrast imaging survey to aid future observers using Keck-NIRC2 in conjunction with the vortex coronagraph in theMsband and conclude by exploring the direct imaging capabilities with JWST to observe Jupiter- and Neptune-mass planets around Wolf 359.